What is a card scheme, and how do Visa and Mastercard make money?
Visa and Mastercard do not lend money, do not hold money, and do not issue cards.
The body that agrees what a plug should look like does not manufacture kettles or generate electricity. It simply decides the shape of the pins, and then every kettle and every socket in the country has to agree with it. There is no obvious way to compete with that, and the fee is a rounding error on every appliance sold.
No money passes through the middle of this picture. That is the business.
What they actually own
Three things, and none of them is money.
The rulebook. Thousands of pages governing what an issuer must do, how long a merchant has to respond to a dispute, what a decline message may contain, and who bears a loss in each of about forty scenarios. When a payment goes wrong, this document decides who pays.
The network. The physical and logical routing that carries an authorisation from a terminal in Kochi to a bank in Frankfurt and back inside two seconds.
The brand. The reason a merchant who has never heard of your bank will accept your card. That acceptance mark is doing an enormous amount of quiet work.
Why it is such a good business
They take a small percentage of a colossal number, and they carry almost none of the risks the participants carry.
They do not take credit risk, because they do not lend. They do not take deposit risk, because they hold nothing. They do not pay for rewards, because issuers do. Their costs barely rise as volume rises, so growth arrives at very high margin.
And their position is close to unassailable in the classic way: merchants accept the cards because consumers hold them, and consumers hold them because merchants accept them. Every new entrant has to solve both sides at once.
Where they are genuinely vulnerable
Account-to-account rails. UPI, Pix, and instant systems generally move money between bank accounts without a card network in the middle at all. Where those systems are strong, the schemes are not so much competed with as bypassed.
This is the real reason the UPI story matters beyond India. It is the first large-scale demonstration that the four-party model is a choice rather than a law of nature.
Where you meet it
The logo in the corner of your card, and every dispute where your bank told you the rules do not allow something and could not tell you whose rules.